The overall objective of the research is to elucidate mechanisms that control lens differentiation. This is important for understanding: (1) how the normal lens forms, (2) how developmental processes are involved in the maintenance of its normal structure and function throughout life. This is basic to understanding developmental and growth abnormalities, and perhaps even more insidious ageing changes that may lead to cataract. There are 4 specific aims for the next 3 year project and these are all concerned with the role of fibroblast growth factor (FGF) in controlling events in lens morphogenesis and differentiation in rats. 1. Analysis of the fibre cell lineage. This involves labelling single epithelial cells in explant cultures with FITC-dextran and monitoring their responses to the factor that stimulates them to differentiate into fibres, FGF. Regular observations of labelled cells in explants exposed to fGF will establish patterns of proliferation and migration. The onset of beta- and gamma- crystallin synthesis in labelled cells will be detected by rhodamine immunofluorescence. 2. Does the response of epithelial cells to FGF change during ageing? The capacities of epithelial explants from different ages of donors to synthesis alpha-, beta- and gamma-crystallins, and undergo migration and proliferation will be measured. Alpha-, beta- and gamma-crystallin accumulation in explants will be measured by ELISA methods. Cell migration will be quantified as described above and cell proliferation will be measured by H-thymidine uptake. 3. Influence of FGF on extracellular-matrix (ECM) synthesis and lens capsule formation. Production of ECM components in explants will be measured as a function of time after addition of FGF. Major ECM components in lens capsule are laminin, collagen type IV, nidogen/entactin and heparan sulphate proteoglycan. All will be quantified by ELISA methods except heparan sulphate which will be measured by incorporation of 3H-glucosamine into glycosaminoglycans. 4. Influence of FGF and ECM on lens morphogenesis and differentiation. Head and trunk ectodermal explants will be grown on coverslips coated with different combinations of ECM components. Characteristic morphological changes and the presence of alpha- crystallin will be used to assess the influence of ECM on lens morphogenesis and differentiation. Experiments will be carried out in the presence and absence of FGF to determine whether FGF induces or influences any early developmental events.